1. Technical Field
This invention relates to constant velocity joints.
2. Related Art
Constant velocity joints have long been known to eliminate the problems of sinusoidal variation of speed between the input driving shaft and the driven shaft when an angle exists between the two shafts. This quality is extremely desirable in front half shafts for front wheel drive motor vehicles where a relatively high angle may exist between the drive half shaft and the driven shaft. Because the driven shaft is connected to suspended steerable wheels, the angle may also vary.
Cross groove style constant velocity joints as well as other types of CV joints use balls interposed between an inner race and outer race to pass torque from one race to the other race. The cage has windows sized to retain the balls. Aucktor style cages with concentric spherical inner diameters and outer diameters have been commonplace. These types of cages have an opening with a diameter that is less that the outer diameter of the inner race. The advantage of this relative geometry of the inner race and cage is that the inner race, once assembled within the cage, is then retained within the cage to entrap the balls and prevent them from falling out. However, the spherical inner and outer diameters also restrict the stroke angle capabilities of the constant velocity joint.
In addition, the cage wall thickness is relatively constant with the inner and outer concentric diameters defining the relatively constant thickness. The cage needs to have strength to retain the balls in position during the operation of the constant velocity joint and as torque transfers through the balls.
In accordance with one aspect of the invention, a constant velocity joint has an inner race, an outer race, and a plurality of torque-transmitting balls disposed in a cage that is interposed between the inner race and outer race. The cage has an outer wall and an inner wall that are non-concentric in cross-section along the central longitudinal axis of the cage. The cage has a variable wall thickness that is greatest in proximity to a ball center plane and tapers toward distal ends of the cage.
Preferably, the outer wall has a cross-sectional radial contour with a radius centered on a line extending through the center point of the cage. The inner wall has a cross-sectional radial contour with a radius centered on a line extending through the center point of the cage. The radius of the inner wall is greater than the radius of the outer wall and has its radial center point linearly offset from the radial center point of the outer wall radius, with both the inner wall radius and outer wall radius being greater than one half of the outer diameter of the cage.